Six-time champion Novak Djokovic says a big-business approach to the Australian Open is testing player welfare to the limit in dangerously hot conditions at Melbourne Park.
Still cooling off after his four-set comeback win against Frenchman Gael Monfils in sweltering 39.9C heat, the 12-time grand slam-winning Serb admitted he had struggled to draw breath at times on Thursday.
"The conditions were brutal," Djokovic told reporters after stepping off the Rod Laver Arena furnace, with 67C recorded at ground level.
"It was a big challenge for both of us to be on the court, to be able to finish the match."
It is unclear whether the Australian Open's extreme heat policy, twice invoked in 2009 and 2014, will be enforced on Friday with the Bureau of Meteorology forecasting a top of 42C in Melbourne.
That decision is made when the ambient temperature surpasses 40C and a wet-bulb reading of more than 32.5C is recorded.
When both these boxes are ticked, matches on outside courts are halted and roofs closed on all three indoor-capable venues.
Asked whether Open officials should have stepped in to postpone his match on centre court, Djokovic said it was a tough call.
"It was right at the limit," the 30-year-old 14th-seed said.
"I think there are certain days where you just have to, as a tournament supervisor, recognise that you might need to give players few extra hours until it comes down."
The superstar Serb, bidding to become the lone man to win seven Norman Brookes trophies, hinted that ticket sales were viewed as more important to increasingly corporate-minded tennis bosses.
"You're a part of the industry," Djokovic said.
"Our sport has become an industry, like most of the other global sports.
"It's more business than a sport. At times I mind that, I don't like that."
But Djokovic, returning to the tour after a season-ending elbow injury in 2017, understood Tennis Australia's decision to push ahead with the schedule.
"People might say, 'well, at this level you have to be ... fit'," he said.
"But I think there is a limit, and that is a level of I guess tolerance between being fit and being in danger in terms of health."
Some umpires shelved the strict 25-second rule of time allocated between points as the heat reached its zenith, but Djokovic wasn't afforded that luxury and copped a violation warning - a decision he took with good grace.
Post-match, Monfils said he felt "super dizzy" for a 40-minute spell, while Germany's Andrea Petkovic told Reuters heat-related fatigue wore her down mentally.
Players weren't the only ones suffering in the summer sun at Melbourne Park.
On show court 3, staff members stepped in to treat a heat-affected young child, who appeared to be five or six years old, with ice packs.
Another mother took her three-year-old child out of the stadium to cool down as the heat became too much to bear, AAP was told.
At 63,561, the crowd for day four was down almost 14,000 across the two sessions compared to last year's figures.
Tennis Australia has been approached by AAP for comment on its heat plan for Friday.
